Engineers and Architects: Sharing Drawings Without Exposing the Client
A building plan can reveal a client's address, a security layout and trade secrets. Learn what a title block shows, why PDF layers return, and what to mask.
A building plan carries more than walls and dimensions. The title block names your client, the site address, and often a stamp with a real signature. Before you attach a PDF to an email, know what is hiding in the file, and who each recipient actually needs to see.
What does a drawing's title block reveal?
The title block sits in a corner of every sheet, built to be read. ISO 7200 sets out the data fields a technical document should carry, from the project name to who approved a revision. That structure makes a drawing easy to identify, for the wrong reader too.
- Client and project name, often printed in full on every sheet
- Site address, sometimes down to the plot or lot number
- Revision table, listing who changed what and when
- Engineer's or architect's stamp, a real signature tied to a licence number
- File path or drawing number left in the PDF properties, a trace of your office server
A logo in the corner names your firm. A stamp names the professional who signed off, tied to a licence number often public. None of this is sensitive alone. Together, it turns an anonymous set of drawings into a file anyone can trace to a named client at a named address.
Why CAD PDF layers are not really gone
Most drawings start in CAD software and get exported to PDF for sharing. That export can carry layers, called optional content in the PDF format. Autodesk's AutoCAD documentation describes a setting for this. It 'adds layer information to the PDF file so that you can turn layers on or off when viewing or printing PDF files.' Hiding a layer before export does not remove it from the PDF.
The same PDF can also carry an external reference file name, a plotter path, or notes from a previous drafter. None of it shows on the printed sheet. A recipient who checks the file properties, or opens a layers panel, sees more than the page in front of them.
When a plan should not leave the office at all
Some drawings carry more than a client's address. A floor plan can show where an alarm panel sits, or where a safe is bolted to the floor. It can also show how a server room is wired for access control. For a bank or a private home, that layout is exactly what a burglar would want. If a sheet shows security systems, ask whether it must leave in full.
- Security-sensitive detail: alarm sensors, safe rooms, camera positions, access-controlled doors
- Unpublished know-how: a proprietary structural detail, an unpatented mechanical system, an efficiency trick refined over years
- Anything a competitor could use in a tender you are also bidding on
This is not only about the client's privacy. A drawing can also hold what EU law calls a trade secret. The Directive (EU) 2016/943 defines a trade secret as information that is not generally known. It must also have commercial value because it stays secret, and its holder must take reasonable steps to protect it.
A know-how detail on a drawing can qualify, but only if your firm actually treats it as confidential. If you are unsure whether a detail counts, ask your professional body or a lawyer who handles intellectual property. The answer depends on the country and the specific case.
What does each recipient actually need to see?
A subcontractor pouring a foundation does not need the electrical layout. A supplier quoting windows does not need the client's name. Sending the whole set out of habit hands over information nobody asked for. Match what you send to what the job actually requires.
| Audience | What to mask | What to keep |
|---|---|---|
| Supplier quoting materials | Client name, site address, other trades' layouts | Dimensions and specs for their own scope |
| Subcontractor, one trade | Unrelated systems, security layout, client contact details | Their own drawings and relevant structural notes |
| Tender or competitive bid | Site address if not yet public, competitor-sensitive know-how | Enough detail for an accurate price |
| Portfolio or case study | Client name, exact address, stamp and licence number | The design itself, once the client has agreed |
| Permit office | Anything not structural or not required by the application | Full technical detail the authority asks for |
Flattening a drawing: what you gain and what you lose
Flattening turns a layered PDF into a single image per page. Every layer, and any text hidden under a title block or a mask, disappears into pixels. A recipient can no longer toggle a layer on, search the text, or copy a dimension by clicking it. For a drawing leaving the office, that is usually the point.
This is the trade-off ONYRI Sanitize is built around. It flattens every page it exports, so hidden CAD layers and the underlying text layer are gone for good. Its 'Draw an area' tool lets you cover a title block, a logo or a stamp by hand. The limit is real: the export is a raster image. Fine vector detail loses precision when you zoom, and large sheets keep the layout of the PDF you gave it.
Keep your vector original. A flattened sheet works for a quote, a permit copy, or a portfolio image. A subcontractor who needs to measure precisely, or a colleague who needs to keep editing the design, needs the DWG file or the layered PDF. Send it through a channel you trust.
A checklist before you send a set of drawings
- 1Check the title block: does this recipient need the client's name and address?
- 2Open the PDF layers panel yourself before you assume a hidden layer is gone
- 3Decide per audience: supplier, subcontractor, tender, portfolio and permit office each differ
- 4Flag anything security-sensitive, such as alarms, safes or access control, and ask if it can be left out
- 5Flatten the sheet you send, and keep the vector original filed separately
Frequently asked questions
- Can I just hide a CAD layer instead of deleting it before I export to PDF?
- No. Hiding a layer changes what is visible, not what is in the file. Autodesk's own documentation confirms a PDF can carry layer information so a viewer can turn layers back on. Delete or purge the layer, or flatten the exported PDF, before you send it.
- What exactly in a title block can identify my client?
- The client's name, project name, and site address are usually printed in full. The revision table can add names of reviewers, and your stamp ties the sheet to your own licence number. Together, that is often enough for a stranger to find the address on a map.
- Is a building plan protected by trade secret law?
- It can be, under the EU Trade Secrets Directive, if it holds know-how that is not public and has value because it is secret. Your firm must also actively protect it. A standard floor plan usually does not qualify. A proprietary structural detail might, and the answer depends on your country.
- Does flattening a PDF drawing hurt its accuracy?
- Yes, a little. Flattening turns vector lines into a fixed-resolution image, so zooming in far enough shows pixels instead of a sharp line. For a quote or a permit copy, that rarely matters. For a subcontractor who measures directly off the file, send the vector original instead.
- Should a subcontractor see the whole set of drawings?
- Usually not. A plumber pricing a bathroom does not need the electrical layout or the client's contact details. Send the sheets that cover their trade, and mask or remove the rest.
Sources & references
- ISO 7200:2004 — Technical product documentation, data fields in title blocks — International Organization for Standardization (ISO)
- PDF Options dialog box — Include Layer Information — Autodesk (AutoCAD help)
- Trade secrets — Directive (EU) 2016/943 — European Commission
- Directive (EU) 2016/943, Article 2 — Definitions — UK National Archives (legislation.gov.uk, reproducing EU law)
Mask a document without uploading it
ONYRI Sanitize finds names, identifiers, bank details and secrets in a PDF, a Word file or a scan, and masks them in your browser. You check the preview, then download a flattened copy.